Motion Detect, sensor pin on off button add?

hello this code shows the motion sensor on the web page. I want to add 1 button, to close the sensor pin. to make the alarm active or passive. how can I do it?

#include <ESP8266WiFi.h>
#include <ESP8266WebServer.h>
#include <WiFiClient.h>

//SSID and Password of your Wifi router on mobile phone access point
const char* ssid = "okhan";
const char* password = "atakan2009";

ESP8266WebServer server(80);//Server on port 80

int sensorVal;//Our sensor value as digital input
int sensorPin = 0;//D14/SDA/D4 or D14/SDA
int butonPin = 2 // GPI02

char* securityStatus ="Secure";
int numhits=0;

//This routine runs when you open its IP in browser
void handleRoot(){

 char html[1000];

 //Build html page refresh every 10 secs
 snprintf(html, 1000,
"<html>\
   <head>\
   <meta http-equiv='refresh' content='10'/>\   
   <title>Evoto Alarm</title>\
   </head>\
   <body>\
    <center>\
     <h1>Evoto Alarm</h1>\
     <p>Alarm Durumu: %s</p>\
     <p>Sensor Durumu: %d</p>\       
    </center>\    
   </body>\
 </html>",securityStatus,numhits
 );
 server.send(200,"text/html",html);//Send web page
  
}



void setup() {
  // put your setup code here, to run once:
 pinMode(sensorPin, INPUT);//configure pin 4 as an input 
 pinMode (butonPin, INPUT);
 Serial.begin(115200);
 WiFi.begin(ssid,password); //Connect to Wifi router

 //Wait for connection
 while (WiFi.status() !=WL_CONNECTED){
  delay(1000);
  Serial.print(".");
 }

//If connection successful show IP Address in serial monitor on Arduino
Serial.println("");
Serial.print("Connected to ");
Serial.println(ssid);
Serial.print("IP Address:");
Serial.println(WiFi.localIP());

server.on("/",handleRoot);
server.begin();//start server
Serial.println("HTTP server started");

 
}


void loop() {
  // put your main code here, to run repeatedly:
 
//Monitor input from PIR sensor
 sensorVal = digitalRead(sensorPin);
 
 if(sensorVal==HIGH){  
    securityStatus="HAREKET ALGILANDI";
    Serial.println("HAREKET ALGILANDI");
    numhits++;
 }
 else{
    securityStatus="GUVENLI";
    Serial.println("GUVENLI");
 }
  
 server.handleClient();//Handle client requests
}